Bought a deleted truck

[2010 Pete ISX]

I just acquired a 2010 Pete with an ISX15 in it. it has been deleted and tuned to 600hp. i want to turn it down, possibly, and make sure the tune isn't putting the engine in major danger. I know nothing about tuning, nor do i really care to know other than it is safe for my engine.

With that being said, please help me figure out what i need to buy and need to do to make sure i get the most reliability out of it, short of returning it to stock emissions.

thanks in advance